1. Field of the Invention
The present invention relates to a test apparatus. More particularly, the present invention relates to a test apparatus that supplies a test signal to a plurality of terminals in common.
2. Related Art
Conventionally, a test apparatus for testing a device under test such as an IC or an LSI has input a test signal output from one driver into a plurality of devices under test in order to test more devices under test by means of a few hardware resources. FIG. 4 is a view showing a configuration of a motherboard 450 and a probe card 455 in such a test apparatus.
The driver 440 is provided in a test module inserted in a test head of the test apparatus, and outputs a common test signal based on a test pattern to test a device under test 50a and a device under test 50b to the device under test 50a and the device under test 50b. 
The motherboard 450 is also referred to as a performance board. The motherboard 450 is installed on the test head of the test apparatus, and transmits a test signal from the driver 440 to the probe card 455 via a transmission channel 460. The probe card 455 is mounted on the motherboard 450, and inputs the test signal input from the motherboard 450 into terminals of the device under test 50a and the device under test 50b via probe pins.
The probe card 455 includes a switch 470 provided between the driver 440 and the terminal of the device under test 50a, a switch 471 provided between the driver 440 and the terminal of the device under test 50b, a transmission channel 480 for connecting the switch 470 and the terminal of the device under test 50a, and a transmission channel 481 for connecting the switch 471 and the terminal of the device under test 50b. The switches 470 and 471 respectively select whether the driver 440 is connected to the terminal of the device under test 50a and the driver 440 is connected to the terminal of the device under test 50b. 
For example, when either of the devices under test 50 is bad as a test result, since this device under test 50 is disconnected from the driver 440, a test for the other device under test 50 can be continued. For example, in a leakage current test for the device under test 50a and the device under test 50b, when a leakage current is detected from the device under test 50b, a leakage current test for the device under test 50a can be continued by disconnecting the terminal of the device under test 50b from the driver 440 by turning off the switch 471.
In addition, since prior art documents are not now recognized, the description related to prior art documents will be omitted.
In the above-described conventional art, in order to raise a quality of a waveform of a test signal supplied to the device under test 50a and the device under test 50b, it is desirable to shorten the transmission channel 480 and the transmission channel 481 and branch a test signal from the driver 440 in the vicinity of the device under test 50a and the device under test 50b. However, the transmission channel 480 and the transmission channel 481 become longer when the switches 470 and 471 such as a relay are provided between the driver 440 and the devices under test 50a and 50b. In this case, since a test signal reflects on a contact portion of the probe card 455 and one of the devices under test 50, a test signal input into the other device under test 50 is disturbed.
For this reason, since a test signal switching at high speed has a significantly deteriorated waveform in the above-described conventional art, it was difficult to supply a high-speed test signal exceeding, e.g., 10 MHz to 30 MHz to a plurality of devices under test.
Moreover, according to the request of multiple pins of the device under test 50 and the increase of the number of the devices under test 50, the number of the necessary switches 470 and 471 increases, and thus it is difficult to mount these switches on the probe card 455. However, when mounting these switches 470 and 471 on the motherboard 450, the transmission channel 480 and the transmission channel 481 become longer similarly to the above, and thus a quality of a waveform of a test signal decreases.